What are the indicators that a large lake once existed in that spot?
Fish bones?
Sunken canoe’s?
Layers of mud?
I always wondered how scientists are able to make these determinations with accuracy.
Fish bones?
Shellfish are more likely, there are species that only live in fresh water.
Layers of mud?
yes, along with wave cut terraces, stranded beaches, and other geological evidence of large amounts of still water.
I saw remnants of such an impoundment from Polychrome in Denali National Park in Alaska. There is clear evidence of areas swept by rushing water, very large and worn boulders in odd places, large scour holes made by these big rocks being roiled around in the same place.
The scale is extremely large,ie miles, but the same phenomena are visible in small streams.